Always clenching the teeth is a kind of mild oral and mandibular dystonia. Dystonia is mainly an excessive contraction of the muscles, resulting in an abnormal posture of a part of the body. Oral and mandibular dystonia is one of them, resulting in the patient’s masticatory muscles continue to contract, the jaw can not open normally, or even open the mouth is less than a cross finger, resulting in the patient can not chew and eat normally, often combined with vocal difficulties, slurred speech, or combined with the eyelid muscle spasm, contraction. It is mostly related to the patient’s emotional anxiety, depression, mental tension and excessive stress, which leads to an imbalance between the excitation and inhibition processes in the cerebral cortex, inducing irregular spasms or contractions of the masticatory muscle movements. Currently, the preferred treatment measure is to apply botulinum toxin to do the local injection treatment of masticatory muscle, which serves to reduce the pathological state of involuntary contraction of masticatory muscle.